Structural distortions and gap states in conjugated polymers

We present a simple scheme that allows for accurate estimates of the energies of orbitals induced by structural defects like solitons and polarons in conjugated polymers. The scheme works within a single-particle framework and by considering solely the band structures of periodic, defect-free polymer chainsʹ. These latter may be obtained using parameter-free computational methods. We illustrate the scheme on four different systems whereby we reproduce well-known results (trans polyacetylene), explain less well-known results (polycarbonitrile), demonstrate that correlation effects may not have to be invoked in order to explain experimental findings (polythiophene), and present an alternative interpretation of experimental results (Pt-polyyne).